Marked N-acetylaspartate and choline metabolite changes in Parkinson's disease patients with mild cognitive impairment

Background: The mild cognitive impairment in Parkinson's disease (PD-MCI) has received increasing attention, of which the diagnosis is challenging. To analyze the possible biomarkers for the early diagnosis, we investigated the metabolite changes in different brain regions of PD-MCI patients as well as appropriate controls by proton magnetic resonance spectroscopy (MRS). Methods: The metabolism in the occipital lobe, posterior cingulate, substantia nigra and basal ganglia was studied in 66 PD-MCI patients, 70 cognitively normal PD patients (PD-CN) and 74 healthy controls. Results: The N-acetylaspartate to creatine (NAA/Cr) ratio in the occipital lobe in PD-MCI patients was lower than that in healthy controls (P < 0.05). In contrast, the choline to creatine ratio in the posterior cingulate was higher in PD-MCI patients than in controls or PD-CN patients (both P < 0.05). No significant metabolite difference in the substantia nigra and basal ganglia was found. Furthermore, the decreases of the ratios of NAA/Cr in the occipital lobe were associated with PD-CN (P < 0.05) and PD-MCI (P < 0.0001) while the increase in the ratio of Cho/Cr in the posterior cingulate was associated with PD-MCI (P <= 0.01). Conclusion: The metabolite changes in the occipital lobe and posterior cingulate occur in the early cognitive impairment phase of PD patients. Such variations can be used as the marker for the detection of PD-MCI. (C) 2012 Elsevier Ltd. All rights reserved.